The invention relates to new laminated materials reinforced by a multi-dimensional structure or fabric; it also relates to the means, particularly a weaving loom, which is specially designed for the production of such a structure.
Laminated materials have been known for a very long time and are formed by superimposed layers of textile materials (fabrics, non-woven, etc. which are impregnated with resin, the assembly undergoing heat treatment, in order to cause the polymerization of the said resin and the hardening of the assembly.
These materials have had many uses, either in the form of planar elements (sheets) or in the form of shaped elements obtained by molding, particularly in the building, automobile, shipping and aeronautical industries.
Hitherto, most laminated materials have been obtained by superposing a plurality of textile layers impregnated with prepolymerized resin. The textile materials used are either laps formed from parallel threads or woven threads. The materials used in such laps are, for example, filaments of glass, graphite, boron, aramide and carbon, or mixtures thereof.
There has also been a proposal to produce textile elements in a form making it possible to obtain laminates having cross sections in the form of I, J, T, .OMEGA., etc. Such materials are usually obtained by superposing a suitable number of textile laps, preferably by interlacing them on a template making it possible to obtain the desired form. Such a superposition of the various layers, which hitherto has been carried out manually, is lengthy and costly and, above all, gives rise to the possibility of errors, since the operator may make a mistake in the number of superposed layers and/or in the orientation of the various layers relative to one another. Consequently, there is a risk of delamination in these materials, and their resistance to shocks is sometimes inadequate.
To overcome this disadvantage, many solutions have been proposed in order to obtain woven or non-woven materials having various forms, these materials subsequently being impregnated with a resin. Such materials having a complex form are intended, above all, to have good acoustic characteristics and to not exhibit a high mechanical performance allowing them to be used as structural pieces.
Thus, for example, U.S. Pat. No. 3,481,427 describes a three-dimensional fabric based on glass filaments, which, after being impregnated with a resin and after polymerization, provides a rigid porous panel having very good acoustic properties. According to this document, it is possible, in a single operation, to weave a "sandwich"-type material, one face of which is porous, while the other face is continuous, these two faces being connected to one another by means of grooves. Such a woven material is not intended to have high resistance, its function being, above all, to ensure good sound absorption.
U.S. Pat. No. 3,700,067 likewise describes a three-dimensional porous fabric which also makes it possible to effect good sound absorption.
U.S. Pat. No. 3,670,504 describes a textile structure, in which concrete can be poured and which can serve for undersea construction work (for example, the structure can be filled with sand and other natural materials). The structure comprises two woven laps which are spaced from one another and through which pass threads interlaced in the laps. These threads are advantageously arranged in parallel rows, to give the structure strength and retain the above-mentioned materials. The textile materials forming such a structure are selected to withstand water and, in particular, are polypropylene or "Nylon". The textile structure described in U.S. Pat. No. 3,670,504 is a three-dimensional porous fabric which is suitable for the uses intended in this patent, but which would not be suitable for producing laminated materials with high mechanical resistance.
U.S. Pat. No. 2,206,698 disclosed blinds comprising two woven bands connected by means of a type of spacer passing through the wefts of the said bands in the manner of a chain. Such an article cannot be compared with a three-dimensional structure intended for the reinforcement of laminated materials.
It has also been proposed in French Patent No. 2,319,727 to produce three-dimensional fabrics making it possible to obtain laminates having a high mechanical resistance and good resistance to shocks and to abrasion. However, the method described in this document makes it possible to obtain blocks which, although capable of being produced in any form, are not three-dimensional textile elements which can be produced continuously on a conventional weaving loom.
As indicated in the introduction of French Patent No. 2,315,562, it was also proposed to produce thick three-dimensional fabrics from a bidirectional cloth obtained by means of a conventional weaving process and comprising warp threads and weft threads, and to entangle a third series of threads with this fabric so formed, in a different direction from the warp and weft directions, by means of a weaving machine or a suitably adapted loom.
In such an embodiment, because the warp and weft threads are interlaced, it is virtually impossible to use fragile fibers, such as carbon or graphite fibers.
Recently, FR-A-2,497,839 proposed a solution making it possible to produce very long shaped elements having, for example, a cross section in the form of an I, T, J, etc. directly on a weaving loom. Such a fabric has a structure of the type illustrated in FIG. 1 and, for example, if it is desired to produce I-shaped material, is composed of a central zone (1) subdivided, on each of its sides into two elementary laps (2, 3, 4, 5). The laps of warp and weft threads forming the central part (1) are bound by means of warp binding threads extending over the entire thickness of the material, while the elementary laps (2, 3, 4 and 5) are bound in the same way by means of additional binding warps. This material, when produced on the loom, takes the form illustrated in FIG. 1, and during its shaping into the form of an I, the elementary parts (2, 3, 4, 5) are folded back laterally, the central part (1) thus forming the branch of the I.
It will be seen that, in such an embodiment, the central part (1) is at least twice as thick as the lateral parts (2, 3, 4, 5), and moreover that, with respect to a weaving width (L), the relative widths of the central part (1) and of the lateral parts (2, 3, 4, 5) are admittedly selectable, as required, but the sum of these widths will always correspond to the weaving width.
Furthermore, in view of their final use, these elements have to be reinforced, essentially in the central part, by means of fabrics of the oblique type, in order to impart properties associated with torsional resistance to these elements.